It is sometimes desirable to apply a linear force using a spring or other source of energy and convert that force into a rotational force. For example, emergency actuators are often spring-powered to close a valve or actuate other equipment in an emergency situation when the normal source of power used to operate the valve or equipment is lost, whether that source of power be hydraulic, electrical, or otherwise. A typical emergency valve actuator, used with a fuel line valve and operated by hydraulic fluid pressure, will be driven by a spring to close the valve, in case hydraulic pressure is lost, in order to avoid fuel leaks.
In other situations, it is desirable to convert a force generated by a spring, compressed air, or otherwise in a linear manner into a rotational force, and vice versa. One such situation is a door closer attached to a door through a lever arm so that when the door is opened, the force applied to the door by the person opening it also rotates an output shaft of the door closer. The rotational force exerted on the output shaft causes compression of a spring inside the door opener; and when the door is released, the stored energy in the compressed spring then causes the output shaft to rotate and apply a closure force on the door through the lever arm. In such a device, it is important to efficiently convert the rotational force on the output shaft to a force sufficient to compress the spring, and then efficiently convert the stored energy in the compressed spring back to a rotational force on the output shaft. Preferably, the door closer should have a very compact design with a short length.
It is also very desirable to have a device with a high torque output which, with high efficiency, converts a force applied in a linear manner to a rotational force, and vice versa. The internal mechanism used in the device to accomplish the conversion should have a low frictional coefficient and should be able to handle large loads without binding. The device should also be able to handle large axial and radial shaft loads. The device should be relatively light in weight and small in size, and be relatively easy and inexpensive to manufacture. The device should have an uncomplicated and strong design to increase reliability, and be usable for heavy-duty applications. The present invention fulfills these needs and further provides other related advantages.